Dye/indicator-HELP

I am looking for a sort of dye and/or indicator reaction in order to
differentiate organisms who produce lactic acid and acetic acid on an
agar. Is that feasible?
Also does anyone out there know any biochemical reaction by which
possessing beta galactosidase can be monitored on an agar, again by using
a dye or an indicator.
Thanks in advance
Hamid